Further contributing to the idea of mTEChi as a functionally mature mTEC subset was the identification of Aire expression in this medullary epithelial subset, the expression of which is a key regulator of the capacity of mTEC to express a defined array of the PTAs expressed within the thymus.[21, 22, 45] The importance of Aire's role in intrathymic PTA expression is demonstrated via the observation that mutations in Aire can lead to targeted autoimmunity against Aire‐dependent self‐antigens. This evidence concerns the gene AIRE and Autoimmunity.